Nanotubes boost shape recovery

February 25/March 3, 2004

Researchers from the University of Dayton,
Miami University and the Air Force Research Laboratory have mixed carbon
nanotubes with polymer to make a plastic that is good at springing back
into shape when heated.

Carbon nanotubes are rolled-up sheets of carbon atoms that are
stronger by weight than steel.

The material would be useful for making large area structures
in space that need to be packaged for launch and then unfurled later,
according to the researchers. It could also be used to make eyeglass frames
that recover their shape and to make temperature-triggered switches.

Adding carbon nanotubes to plastic increases the material's rubbery
modulus and electrical conductivity without changing the elongation and
toughness properties of the plastic, according to the researchers.

Shape recovery occurs when these materials are heated, which melts
polymer crystallites that form when the material is bent. The light-absorbing
and electrical characteristics of the nanotubes enabled the researchers
to heat the material by applying light or current directly to it rather
than using an external heater.

The shape memory polymers could be used in practical applications
in five years, according to the researchers. The work appeared in the
January 25, 2004 issue of Nature Materials.